Flexible partition for stock vats



Aug. 8, 1961 Filed April 20, 1960 R. WELLS 2,995,187

FLEXIBLE PARTITION FOR STOCK VATS 3 Sheets-Sheet 1 INVENTOR Roger WellsBY $21. CD. +z oc: s

ATTORNEY 1961 R. WELLS 2,995,187

FLEXIBLE PARTITION FOR STOCK VATS Filed April 20, 1960 3 Sheets-Sheet 2mm v M v i I IIB J; I I W I I INVENTOR Roger Wells los BY *fi b.1120 F IG a 7' ATTORNEY Aug. 8, 1961 w Ls FLEXIBLE PARTITION FOR STOCK VATS 3Sheets-Sheet 5 Filed April 20, 1960 FIG INVENTOR Roger Wells FIG.|2.

ATTORNEY FIG.I3.

United States Patent 2,995,187 FLEXIBLE PARTITION FOR STOCK VATS RogerWells, Stamford, Conn., assignor to Diamond National Corporation, NewYork, N.Y., a corporation of Delaware Filed Apr. 20, 196i), Ser. No.23,432 21 Claims. (Cl. 162--390) This invention relates to partitionsfor stock vats of rotary pulp molding machines. More particularly, theinvention relates to flexible partitions for dividing a pulp stock vatof a rotary pulp molding machine into a plurality of separatecompartments adapted to contain different kinds or grades of pulp stock,for use in the production of multi-ply molded pulp articles composed ofa plurality of successively deposited superposed different layers.

In the manufacture of many molded pulp articles, particularly foodtrays, pie plates and other types of containers, it is often desirableto provide such articles with a multi-ply structure wherein differentkinds or grades of pulp are successively deposited in well definedseparate layers inter-felted into a composite multi-ply article. Forexample, in a two-ply molded pulp pie plate, the bottom layer may becomposed of a coarse grade of ground wood pulp stock, and the top layermay be composed of a fine grade of sulfite pulp stock possessing highwhiteness and containing a sizing agent which imparts a smooth surfacefinish thereto. It may also be desirable in some instances toincorporate differently colored dyes into the top and the bottom layersto impart a distinctive appearance to the multi-ply articles.

A specific type of molded pulp container in which a multi-ply structureis desirable, has become increasingly important commercially, namely,the molded pulp food trays utilized for the packaging and sale of meat,poultry and the like, in retail food markets. These food trays usuallytake the form of a relatively shallow, generally rectangular container,and a transparent covering sheet of cellophane or polyethylene may bewrapped around the tray and heat sealed to the bottom thereof. Such foodpackages present an attractive display while providing adequateprotection during the sale and temporary storage of the food,particularly for naturally wet or juicy fresh poultry, such as chickensections. It is important for these trays to be capable of absorbing anyexuded blood, natural juices or other free fluids, and to prevent suchfluids from being free to run around the inside of the sealed foodpackage during normal handling by prospective purchasers. For thispurpose, the multiply tray may be composed of an outer layer ofnonabsorbent molded pulp, and an inner layer of absorbent pulp may beprovided to soak up the above mentioned free fluids. Preferably thisinner layer is provided with a plurality of small cup-shaped depressionsadapted to serve as fluid traps. These depressions may be formedsimultaneously with the molding of the main body of the tray byattaching to the usual drainage screen on the forming face of the pulpmold a plurality of uniformly spaced solid projecting nubbins made ofmetal, rubber or a suitable plastic. Details of certain features of suchmolded pulp containers, and molds and methods for making them, aredisclosed and claimed in co-pending application Serial No. 793,819,filed February 17, 1959, titled Molding Pulp Articles HavingDepressions, also naming Roger Wells as inventor.

Multi-ply molded pulp articles have customarily been manufactured bysuccessive dipping a formaninous mold into a series of tanks or vats,each containing different grades or kinds of pulp stock, to accrete bysuction deposition the successive different layers of pulp on the mold.Usually, these vats of pulp slurry have been separately spaced units,and the mold or a series of molds have been advanced into and out of thetanks in a plurality of separate successive operations. Efforts havebeen made in the past to produce multi-ply molded pulp articles on arotary molding machine within a single pulp stock vat, by providingpartitions intended to subdivide the vat into a plurality of separatecompartments adapted to containv different pulp stocks, through which aseries of molds are advanced successively during rotation of themachine. However, in these prior art machines considerable diflicultywas generally encountered in attempting to provide partitions capable ofeffectively preventing intermixing of the different pulp stocks from theseparate compartments as the series of molds were advanced therethrough.

An object of the present invention is to provide new and improvedapparatus for molding mul-ti-ply pulp.

articles.

Another object of the invention is to provide new andimproved partitionsfor stock vats used in the production of multi-ply pulp articles onrotary pulp molding machines.

Still another object of the invention is to provide new and improvedpartitions for maintaining sealing contact with a series of molds beingadvanced successively through a compartment containing pulp stock, inthe operation of a rotary pulp molding machine.

Yet another object of the invention is to provide flexible partitionsfor dividing a stock vat of a rotary pulp molding machine into separatecompartments, and for maintaining sealing contact with a series of moldsbeing advanced successively through the separate compartments, toprevent interrnixing of the ditferent pulp stocks in the production ofmulti-ply molded pulp articles.

Other objects and the nature and advantages of the instant inventionwill become apparent from the following detailed description, taken inconjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view, partially in section, of

a rotary pulp molding machine including a stock vat divided intoseparate compartments by a partition embodying the present invention;

FIG. 2 is a vertical sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a side elevation view of a partition representing a secondembodiment of the invention;

FIG. 4 is a side elevation view of a partition representing anotherembodiment of the invention;

FIG. 5 is a fragmentary vertical sectional view of a foraminous suctionmold provided with a plurality of projecting nubbins for producingmulti-ply molded pulp trays having cup-shaped depressions formedtherein,

which mold is shown in sealing contact with a partition embodying theinvention;

FIG. 6 is a fragmentary top plan view of a portion of a molded pulp trayproduced by the pulp mold shown in FIG. 5;

FIG. 7 is a vertical sectional view taken along the FIG. 12 is a planview of a portion of the partition.

shown in FIGS. 10 and 11; and

FIG. 13 is a plan view of another portion of the partion of FIGS. and11.

In accordance with certain features of the invention, in a rotary pulpmolding machine for producing multiply molded pulp articles, saidmachine including a rotatable drum having a plurality of foraminousmolds mounted on its periphery, and a pulp stock slurry vat in which thedrum is partially immersed for advancement of the molds therethrough, aflexible vertical partition is mounted in the vat for dividing the vatinto a plurality of separate compartments adapted to contain differentpulp stocks through which the molds are advanced successively duringrotation of the drum, said flexible partition being in liquid sealingtangential wiping contact with the portions of the drum and molds beingadvanced therepast, thereby effectively preventing intermixing of thedifferent pulp stocks in the compartments separated by the partition. Inone embodiment of the invention the flexible partition is in lightlywiping liquid sealing contact with the drum and the molds, while inanother embodiment of the invention wherein the molds are provided withprojecting nubbins for producing cupshaped depressions in the pulparticles molded thereon, the flexible partition is adapted to scrape theadvancing nubbins as well as form wiping sealing contact therewith.

Referring to FIGS. 1 and 2, a plurality of conventional foraminoussuction molds 20 are mounted at equal intervals circumferentially spacedaround the periphery of a cylindrical drum 22 mounted above andpartially submerged within a pulp stock slurry tank 24 for rotationabout a horizontal axis therein. Each of the molds 20 communicatesthrough one of a plurality of radial channels 26 with a central hollowshaft 28 extending axially through the drum 22 and communicating with anexterior source of suction (not shown). Suitable driving means (notshown) operatively connected to the shaft 28 is provided for rotatingthe drum 22 either continuously or intermittently. During the rotationof the drum 22 the molds 20 are advanced successively through liquidpulp stock slurry contained within the vat 24, while suction applied tothe molds 20 through the channels 26 during immersion of the molds 20,causes pulp fibers to be extracted from the slurry and deposited ontothe forming surfaces of the molds 20, thereby forming initially moldedpulp articles known as preforms. In the usual manner, the suction iscontinued while the molds 20 are advanced upwardly above the slurry toextract excess moisture from the preforms until the molds reach atransfer mechanism indicated generally at 30, where the suction on thesuccessive molds 20 is shut off momentarily while the transfer mechanism30 removes the preforms therefrom.

The transfer mechanism 30 is shown only schematically, and it isintended to be conventional in construction. This mechanism includes aplurality of dies 32 contoured to fit snugly against the successivemolds 20 to remove the pulp preforms therefrom when suction is appliedto the dies 32. A rotatable die carrier 34 on which the dies 32 aremounted radially is positioned adjacent to the drum 22 and mounteddirectly over one end of a conveyor belt 36, adapted to transport thesuccessive pulp preforms to a drying oven (not shown).

Although the molds 20 are shown located at twelve equal intervals on theperiphery of the drum 22, it is evident that the number of intervals maybe varied from fewer to many more than twelve, depending upon the sizeof the drum and the size and spacing of the molds. At each of theseintervals four of the molds 20 may be mounted in a row as shown in FIG.2, or any convenient number from only one to many more than two of themolds may be mounted at each interval on the periphery of the drum 22.Instead of employing the drum 22, a wheel or any other suitable type ofconveyor may be employed to advance the molds successively through thevat 24.

Multi-ply molded pulp articles are formed on the molds 20 bysuccessively depositing at least two different layers of pulp fibers onthese molds as they are advanced through the vat 24. For a two-plymolded pulp article this result is achieved by subdividing the tank 24into two separate sections or compartments 38 and 39, each of which isadapted to contain a slurry of a different pulp stock. During clockwiserotation of the drum 22, as viewed in FIG. I, the molds 20 are advancedin succession through the vat 24 in an arcuate path, first passingthrough the compartment 38 wherein a slurry of one kind or grade of pulpstock is maintained, and then advancing through the compartment 39 wherea slurry of a difierent pulp stock is present. The slurries in the twocompartments 38 and 39 may be composed of dilute fibrous dispersions inwater of distinctly different grades of pulp stock in suitableconcentrations, or they may be of the same grade of pulp stock indifferent concentrations, or differently colored, or one slurry maycontain a sizing agent while the other may not. Although only twocompartments or sections of the vat 24 are present in the apparatusshown in FIG. 1 to illustrate the principles of the invention, it isapparent that three or more compartments could be provided in differentportions of the vat 24, if desired, to produce multi-ply molded pulparticles having the corresponding number of plies.

In accordance with the present invention, a flexible vertical partition40 is mounted within the pulp slurry vat 24 and extends transverselythereacross, as shown in FIG. 2, thereby subdividing the vat 24 to formthe separate compartments 38 and 39 thereof, for the purpose ofmaintaining separation between the compartments 38 and 39 and preventingany intermixing of the different pulp stocks contained therein. Thelower end of the vertical partition 40 is secured to a base bar 42extending transversely across the inside of the bottom of the vat 24,and the partition 40 may be removably attached to the base bar 42 bymeans of a plurality of spaced bolts 44, or other suitable fasteners.The upper end of the vertical partition 40 is bent over into asubstantially horizontal position, wherein the end portion thereof is intangential contact with the surfaces of the molds 20 being advancedtherepast, and this end of the partition 40 is in lightly wiping liquidsealing contact therewith. At least the upper portions of the partition40 should be sufficiently flexible to conform generally to the irregularsurface defined by the molds 20 and by the intervening and surroundingportions of the surface of the mold carrier drum 22, as is best shown inFIG. 2. Preferably, the flexible partition 40 is composed of relativelythin, impervious, rubber sheet material. For example, the partition 40may be made of a flexible rubber sheet having a thickness of about /4inch and a length of about 3 inches, of which the last inch of the upperend thereof is in tangential sealing contact with the advancing molds20.

It is evident that one of the principal difficulties encountered inattempting to prevent intermixing of the pulp stocks contained in thecompartments 38 and 39 is the possibility of having small quantities ofthe stock in the compartment 38 being swept into the compartment 39 bythe molds 20 projecting from the periphery of the drum 22. Similardifficulties may be expected at opposite ends of the drum 22, where someclearance is usually provided between the ends of the drum 22 and theside walls of the slurry bath 24. In order to overcome thesedifficulties, the peripheral surface of the drum 22 is provided withfiller bars 46 mounted between each adjacent row of the molds 20thereon. The filler bars 46 may project radially outwardly from thesurface of the drum 22 the same distance as that of the molds 20 thereonor a trifle less. Thus, as the flexible upper end of the partition 40contacts the successive molds 20 being advanced therepast duringrotation of the drum 22, the filler bars 46 mounted intermediateadjacent successive 'molds 20 allows the upper end of the partition 40to conform more closely to the surfaces of the molds 20 and'the drum22'. Likewise, opposite ends of the-drum 22 may be provided with a pairof annular radially mounted skirts 48, which are wiped in sealingcontact by a pair of flexible vertical blades 50 mounted on the sides ofthe vat 24 directly above the vertical partition 40 and forming anupwardly extending continuation thereof.

The force of the tangential sealing contact between the upper end of theflexible partition 40 and the contoured surfaces of the advancing molds.20 and the. adjacent portions of the periphery of the drum 22 should besufficiently light to wipe in liquid sealing contact therewith, withoutactually scraping the said surfaces of the molds and drum. At this stageof the molding operation, the freshly deposited layer of pulp fibersbeing formed on the molds 20 is quite soft and pliable, being almostgelatinous in consistency and having comparatively little resistance toabrasion. Hence, any scraping or strong rubbing action by the flexible.partition 40 against this pulp deposit is likely to rub off some of thedeposit, possibly form it into balls and blobs, and form score marks inthe deposit. It is also likely that the scraping effect would producenon-uniform thicknesses in the resultant molded pulp articles.Therefore, when the flexible partition 40 is in direct wiping contactwith the freshly deposited layer of molded pulp, as it is in theembodiment of the invention illustrated in FIGS. 1 and 2, the force ofcontact should be merely a lightly wiping contact. It is evident thatthe surfaces of the flexible partition 4%) itself should be smooth andpolished to prevent scoring and scraping effects.

Due to the fact that suction is constantly applied to the molds 20during the entire time they are being advanced through the compartments38 and 39, and While they are in wiping contact with the upper end ofthe flexible partition 40, the suction being applied internally to themolds 20 has the effect of pulling the contacting upper end portion ofthe flexible partition 40 towards the mold surfaces. One result ofpulling of the free, flexible upper end of the partition 40 towards theadvancing molds 20 in this manner, is the bending of this end of thepartition 40 into conformity with the contour of the surfaces of theadvancing molds 20 and the maintenance of a liquid-tight seal therewith,and since the partition is impervious, thereby preventing intermixing ofthe pulp stock from the separate compartments 38 and 39. Anotherimportant result of having this end of the flexible partition 40 pulledtowards the advancing molds 20, is the fact that the pressing of thecontacting end of the partition 40 against the freshly deposited layerof pulp fibers squeezes some of the excess water. out of the depositedpulp and smoothens the surface thereof. In addition to its desirablesmoothening effect on the deposited pulp fibers, this squeezing actioncauses the deposited pulp fibers to become denser and firmer, therebyimproving the appearance and strength of the molded pulp product. Anyreduction in excess moisture at this stage of the molding operations hasthe effect of speeding up final drying operations, which are eventuallynecessary to remove all excess moisture, thereby effecting importanteconomies in production costs.

Referring again to FIG. 1, a fresh supply of pulp slurry may beadmitted, when needed, to the compartment 38 through a supply pipe 52,and similarly a supply pipe 54 is provided to supply pulp slurry asneeded to the compartment 39. These supply pipes 52 and 54 may beprovided with float control valves (not shown) to maintain the slurriesin the compartments 38 and 39 at the desired constant levelautomatically. The upper level of the slurries in the two compartments38 and 39 may be maintained at approximately equal heights above thebottom of the vat 24, but it is preferred to have the slurry in thecompartment 39 maintained at a higher level than that of-the'compartment 38, asiis illustrated in FIG. 1,

in order to create a differential in hydrostatic pressure. Thisdiflerence in hydrostatic pressure assists in pressing the free upperend of the partition 40:

therebetween.

towards the advancing molds 20, and it also helps to further. minimizepossible intermixing of the two different pulp stocks, since there wouldbe less pressure in the compartment 38 from which the slurry wouldnormally have a tendency to flow into the compartment 39 duringclockwise rotation of the drum 22.

When only light wiping contact is desired between theflexible partition40 and the surfaces of the advancing molds 20 and drum 22, withoutscraping or strong rubbing contact therebetween, the entire partition 40may be made from a relatively thin flexible sheet composed of rubber orother suitable plastic materials, which construction is suitable for theembodiment of the invention illustrated in FIGS. 1 and 2. Of course,only the upper end portion of the partition 40 need be very flexible forthis purpose, and the lower end portion of the partition 40 where it issecured to the base bar 42, may be relatively inflexible and thick.

In FIGS. 3 and 4, there are shown specific alternative embodiments ofthe invention wherein greater flexibility is imparted to the upper endof the partition than tothe lower end thereof. In FIG; 3 there is showna flexible partition 60 of gradually tapered construction, which isadapted to be incorporated into a rotary pulp molding machine in thesame manner as the previously described partition 40. The partition 60is secured at its lower end to a base bar 62, corresponding to thepreviously described base bar 42., by means of a plurality of bolts, ofwhich only one bolt 64 is shown. The partition 60 is made of flexiblesheet material which diminishes gradually in thickness as it tapers fromits lower end to its upper end. One possible Way of attaining thedesired taper in the construction of the partition 60 is by moldingrubber, polyethylene, polystyrene, or other suitable plastics, to form atapered solid, flexible sheet thereof. However, it is preferred toconstruct the tapered partition 60 by consolidating a plurality offlexible, resinimpregnated. sheets of graduated length to form acomposite tapered laminate, such as a laminate of resin-impregnatedglass cloth.

In the embodiment of the invention illustrated in FIG. 4, a flexiblepartition 70 is secured to a base bar 72 by means of a plurality ofbolts, of which only one bolt 74 is shown, in the same manner as thepartition 60. The partition '70 includes a relatively stiff lowerportion 76, which may be made of rubber sheeting about Mr inch thick,and an upper portion '78 of the partition 70. is formed by a relativelyflexible thin sheet of rubber, polyethylene, or the like, which isattached to the thicker rubber bottom portion 76 by means of a pluralityof spaced fasteners, of which only one fastener 79 is shown. Therelatively thin, flexible upper portion 78 of the partition 70 may havea thickness ranging from about .008 inch up to about .020 inch, and thesurfaces thereof should be relatively smooth and polished.

FIG. 5 shows a relatively stiff, flexible partition 80 having its lowerend secured to a base bar 82 by means of a plurality of spaced bolts, ofwhich a bolt 84 is shown, which partition 80 is adapted to be mountedwithin a slurry vat 85 in the previously described partitions 40, 60 and70. The upper end of the partition 80 is bent over into a substantiallyhorizontal position in tangential contact with the forming face of aforaminous suction mold 86 being advanced therepast. The mold 86comprises a standard perforated forming plate 88 contoured to form amolded pulp tray thereon. A foraminous wire mesh straining screen 90covers the forming face of the perforated plate 88 and the screen 90 issecured around the periphery of the plate 88 by means of a retainingring '92, which is attached thereto by a plurality of bolts, of whichone bolt 94 is shown. The mold 86 corresponds 7 generally in structureand in function to one of the molds shown in FIGS. 1 and 2, but the mold86 is provided with a plurality of solid projecting nubbins 96 securedat intervals to the screen for forming depressions in pulp trays beingmolded on the mold 86.

In FIGS. 6 and 7, there is shown a molded pulp tray 100 having aplurality of spaced cup-shaped depressions 102 therein, which isrepresentative of the type of molded pulp articles having depressionsformed therein which are producible by foraminous suction molds havingprojecing nubbins, such as the mold 86 and its projecting nubbins 96.The tray 100 is two-ply in construction, and it includes an upper ply orlayer of absorbent molded pulp 104 and a lower ply or layer ofnon-absorbent molded pulp 106. The cup-shaped depressions 102 are formedin and extend entirely transversely through the absorbent pulp layer 104in that portion of the tray 100 constituting the inside bottom thereof.

In the particular tray 100 illustrated in FIGS. 6 and 7, the cupshapeddepressions 102 formed by the projecting nubbins 96 of the mold 86 mayhave certain critical dimensions so that these depressions 102 arecapable of functioning as mechanical fluid traps in the completed tray100. However, the formation of the cup-shaped depressions 102 isdescribed merely to illustrate the principles of the present invention,and it should be understood that molded depressions in the form ofapertures or perforations having any desired size or shape may beproduced in a similar manner by suitably arranged projecting nubbins.

In the molding of the tray 100, the mold 86 is advanced from right toleft, as viewed in FIG. 5, past the flexible, vertical partition 80, andthe layer 104 is formed first by suction deposition onto the screen 90and the projecting nubbins 96. The flexible partition 80 forms aliquid-tight seal with the mold 86 during the advancement thereof, andthe partition 80 is also in scraping or strongly rubbing contact withthe projecting nubbins 96 on the mold 86. Due to this arrangement, anyportion of the first deposited pulp layer 104 which happens to projectbeyond the nubbins 96 is evenly scraped off by the partition 80 as thenubbins 96 advance therepast. During continued movement of the mold 86beyond the flexible partition 80, the pulp layer 106 is graduallydeposited on top of the previously deposited layer 104. Due to the cleanscraping action of the partition 80 in removing any excess portion ofthe layer 104 projecting beyond the nubbins 96, and the fact that thepartition 80 forms a liquid-tight seal effectively preventingintermixing of the different pulp stocks on opposite sides thereof, theboundary line between the layers 104 and 106 in the completed compositemolded pulp tray 100 is quite sharp and well defined. It is evident thatthe projecting nubbins 96 hold the flexible partition 80 away from theperforated forming plate 88 and the straining screen 90 at a fixeddistance therefrom, thereby preventing complete removal of the initiallydeposited pulp layer 104. Furthermore, such scraping or strong rubbingaction could not be tolerated in the case of the molds 20 which lack anyprojecting nubbins, and only light wiping action, such as is obtainablefrom the partitions 40, 60 or 70, is acceptable when no projectingnubbins are present on the molds.

Similar scraping or strong rubbing action is obtainable from a flexiblepartition 110 shown in FIGS. 8 and 9, in the form of an expansible,flexible diaphragm of sheet material. Opposite side edges of thepartition 110 are secured to a plurality of spaced base bars 112 bymeans of a plurality of fasteners 114, thus forming the sheet materialinto a generally vertically disposed curved loop. The partition 110extends entirely transversely across a stock vat 115, which is providedwith inlet pipes 116 adapted to admit compressed air, or other fluidunder 8 admission of fluid pressure in this manner causes the centralportion of the partition 110 to rise upwardly and press into closeconformity with the surface of a mold 118 being advanced therepast. Themold 118 corresponds generally to the mold 86, and it includes aperforated forming plate 120 having a straining screen 122 mountedthereon, and a plurality of projecting nubbins 124 are secured to thescreen 122 at intervals thereon. When the diaphragm type partition 110is expanded, it forms a liquid tight seal with the mold 118, and itpresses in scraping or strongly rubbing engagement with the projectingnubbins 124. In view of the great amount of wear likely to result fromthe rubbing and scraping contact of the partition 110 with theprojecting nubbins 124, it is desirable to construct these members fromrelatively tough, wear-resistant, smooth-surfaced plastic material, suchas neoprene. In addition, a thin film 126 of an extra tough, flexible,wear-resistant, smooth-surfaced sheet material may be interposed betweenthe upper portion of the partition 110 and the projecting nubbins 124.One edge of the film 126 may be anchored to the bottom of the slurry vat115 by a fastener 128, while the opposite edge of the film 126 extendsin the direction of movement of the mold 118, and this edge of the film126 is free to flex to conform to the contour of the mold 118.

An important advantage accruing from the expansible characteristic ofthe flexible diaphragm 110 is the fact that a liquid-tight seal may bemaintained against the mold 118, thereby positively preventingintermixing of the different pulp stocks maintained on opposite sides ofthe partition 110, regardless of the presence or absence of internalsuction applied to the mold 118 during molding operations thereon. Theliquid-tight seal is maintained by the expansible partition 110independently of any difference in hydrostatic pressure of the slurriesof the two different pulp stocks. Moreover, the inflatable, flexiblenature of the partition 110 enables it to fit into close conformity withthe contour of a row of the molds 118 over the entire contacting areatherebetween.

The expansible partition 110, either by itself or combination with theprotective, wear-resistant film 126, exerts a definite scraping orstrong rubbing action against the projecting nubbins 124 of the mold 118being advanced therepast, when the partition 110 is in an expandedcondition during molding operations. Thus, the embodiment of theinvention represented by the expansible partition 110 is designed forthe construction of molded pulp articles having depressions formedtherein, such as the tray 100 illustrated in FIGS. 6 and 7.

Still another embodiment of the invention is illustrated in FIGS. 10,11, 12 and 13, wherein a flexible, vertical partition, indicatedgenerally at 140, is adapted to exert light wiping contact with asuccession of advancing molds which lack projecting nubbins as do themolds 20. The lower end of the partition is secured to a base bar 142 bymeans of a plurality of fasteners 144, in a manner similar to that inwhich the partitions 40, 60, 70 and 80 are mounted. The partition 140 ismade up of three separate superimposed thin sheets 146, 147, and 148,which are joined together at their lower ends by the fasteners 144.These sheets are quite flexible and thin, and they are preferablycomposed of a smooth surfaced, tough, wear-resistant plastic material,such as Mylar film. The three separate sheets constituting the partition140, are mounted in light wiping contact with different portions of aplurality of suction molds mounted on the periphery of a rotatable drum152, of which only a fragment is shown, corresponding to the molds 20and the drum 22 of FIGS. 1 and 2. The molds 150 are each provided withperipheral retaining rings 154, which are secured to the drum 152 bymeans of spaced bolts 144. During rotation of the drum 152 to advancethe molds 150 from right to left, as viewed in FIG. 11, the sheets 146,147 and 148 are contacted successively by the mold 150 in the order inwhich the sheets are enumerated.

First, the sheet 146 is wiped by each of the successive molds 150, andthe upper end of this sheet is provided with a perfectly straighthorizontal edge 158 arranged to engage only the projecting forming facesof the molds 150, without touching the retaining rings. 154 or thesurface of the drum 152. Next, the intermediate sheet 147 is reached bythe successive molds 150 immediately after they have advanced beyond thesheet 146. This intermediate sheet 147 is provided with a plurality ofupwardly projecting tabs 16%) formed on an otherwise straight upper edge161, which tabs are arranged to wipe that portion of the molds 150intervening between the projecting forming faces thereof and theretaining rings 154. Pinally, the sheet 148 is provided with a pluralityof upwardly projecting tabs 162 adapted to wipe the surface of the drum152 in between the retaining rings 154 of adjacent molds 150 just afterthe sheets 146 and 147 have been passed by the molds 1519. Thus, byproviding the freely flexible upper ends of each of the three sheets146, 147 and 148 with a different special configuration, these sheetscooperate to conform closely to the contoured surfaces of the molds 150and the drum 152 advancing therepast, and to engage said surfaces inlightly wiping tangential sealing contact.

In order to impart some stiffness to the lower end of the flexiblepartition 14%, for the same reason this is done in the construction ofthe partitions 60 and 70, a relatively stiff loop 166, formed by foldinga strip of canvas or rubber sheeting upon itself, is secured by thefasteners 144 to the base bar 142 behind the lower ends of the sheets146, 147 and 148. The relatively stiff loop 166 provides a resilientbacking for the very flexible thin sheets 146, 147 and 148, whichassists in holding these sheets vertically disposed in wiping contactwith the molds 150 and the drum 152,.

Apparatus embodying the invention enables multi-ply pulp articles to bemolded in a single slurry vat, by effectively subdividing the vat intoseparate compartments adapted to contain slurries of different pulpstocks, through which a series of molds may be advanced successivelywithout causing intermixing of the different pulp stocks. The pulparticles produced are characterized by improved density and smoothness,and the boundaries between the plies of the articles are clearlydefined.

Although the invention has been illustrated and described withparticular reference to rotary pulp molding machines of the typerepresented by a rotatable drum having a plurality of foraminous suctionmolds projecting from its periphery, it is contemplated that flexiblepartitions embodying the invention may be incorporated into stock vatsof other types of rotary pulp molding machines, such as the well knowncylinder machines, pressure formers and rotary filters. In such otherpulp molding machines, flexible partitions embodying the presentinvention may serve, not only as dividers between two adjacentcompartments of a stock vat, but also as a terminal partition for oneend of an uncompartmented stock vat.

It will be obvious to those skilled in the art that various changes maybe made without departing from the spirit of the invention and,therefore, the invention is not intended to be limited to what is shownin the drawings and described in the specification but only as definedin the appended claims.

What is claimed is:

1. In apparatus for molding multi-ply pulp articles, including arotatable drum means having a plurality of foraminous suction moldsmounted on its periphery for rotation through a pulp slurry vat mountedbelow the drum means, and a plurality of separate compartments providedin the vat adapted to contain slurries of different pulp stocks throughwhich the molds are advanced successively during rotation of the drummeans, the improvement comprising a flexible vertical partition mountedin the bottom of the vat and extending extirely transversely thereacrossbetween said compartments, and the upper" portion of said verticalpartition being mounted in liquid sealing tangential wiping contact withthe surfaces of the drum means and the molds advancing therepastduringrotation of the drum means, thereby effectively preventingintermixing of the different pulp stock slurries contained in theseparate compartments,

2; The structure of claim 1; said drum means including filler bar meansinterposed between adjacent sue tion molds and projecting outwardly fromsaid drum means substantially the same distance as said molds wherebysaid flexible partition will sealingly engage said filler bar means andsuction molds with a minimum of distortion thereof to aid in preventingintermixing of said different pulp stock slurries in the separatecompartments.

3. The structure of claim 1; said vat including flexible sealing bladesat opposite sides thereof and sealingly engaging adjacent sides of saiddrum means for aiding to prevent intermixing of said different pulpstock slurries in the separate compartments.

4. The apparatus defined by claim 1, wherein the vertical partition isconstructed from a relatively thin,

flexible, smooth-surface sheet material, having its lower end secured tothe inside bottom of the slurry vat, and having its upper end freelyflexible in lightly wiping liquid sealing contact with the surfaces ofthe drum means and the molds advancing therepast.

5. The apparatus defined by claim 4, wherein the vertical partition ofsheet material is tapered lengthwise so that it diminishes gradually inthickness from its secured lower end to its freely flexible upper end.

6. The apparatus defined by claim 5, wherein the tapered verticalpartition of sheet material is a composite laminate constructed from aplurality of consolidated resin-impregnated sheets graduated in length.

7. The apparatus defined by claim 4, wherein the vertical partition isprovided with a relatively stiff lower portion constructed from arelatively thick sheet material having its lower end secured to theinside bottom of the slurry vat, and the upper portion of the partitionis constructed from a relatively thin, flexible, smoothsurfaced sheetmaterial.

8. The apparatus defined by clm'm 4, wherein the vertical partition isconstructed from a plurality of separate superimposed thin sheets joinedtogether at their lower ends, said sheets having differently contouredupper edges adapted to engage different portions of the surfaces of thedrum and the molds advancing therepast.

9. The apparatus defined by claim 8, wherein the vertical partition isconstructed from three separate superimposed thin sheets, the upper edgeof one of said sheets being substantially entirely straight transverselyacross the vat and adapted to contact only the outermost projectingsurfaces of the molds, and the upper edges of the other two sheets beinggenerally straight but having projecting tab portions adapted to contactthe periphery of the drum means and the other surfaces interveningbetween adjacent molds on the drum means.

10. In apparatus for molding multi-ply pulp articles, including arotatable drum having a plurality of foraminous suction molds mounted onits periphery for rotation through a pulp slurry vat mounted below thedrum, said molds having a plurality of nubbins projecting from theforming face thereof for forming depressions in pulp articles moldedthereon, and a plurality of separate compartments provided in the vatadapted to contain slurries of different pulp stocks through which themolds are advanced successively during rotation of the drum, theimprovement comprising a flexible vertical partition mounted in thebottom of the vat and extending transversely thereacross between saidcompartments, the upper portion of said vertical partition being mountedin tangential scraping contact with the projecting nubbins on the moldsadvancing therepast during rotation of the drum, and said partitionbeing in liquid sealing wiping contact with the surfaces of the drum andthe molds thereby effectively preventing intermixing of the differentpulp stock slurries contained in the separate compartments.

11. The apparatus defined by claim 10, wherein the vertical partition isconstructed from a relatively thick, flexible, smooth-surfaced sheetmaterial, having its lower end secured to the inside bottom of theslurry vat, and having its upper end free to flex in liquid sealingscraping contact with the mold and nubbin surfaces advancing therepast.

12. The apparatus defined by claim 10, wherein the vertical partition isan expansible flexible diaphragm having its opposite edges secured tothe inside bottom of the slurry vat, and means for admitting fluid underpressure into the interior of the diaphragm to cause expansion thereof,thereby urging the upper portion of the expanded diaphragm into liquidsealing scraping contact with the mold and nubbin surfaces advancingtherepast.

13. A partition for stock vats of rotary pump molding machines includinga series of foraminous suction molds mounted on the periphery of arotatable drum means for movement in succession through pulp stockslurry contained in a vat thereof, comprising a flexible sheet ofsmooth-surfaced impervious material disposed generally vertically andextending entirely transversely across the stock vat, and means forremovably securing the lower end of the sheet to bottom of the stockvat, the upper end of said sheet being unsecured, freely flexible, andbeing bent over into a generally horizontal position in liquid sealingtangential wiping contact with the surfaces of the drum means and themolds advancing therepast.

14. The partition defined by claim 13, wherein the sheet of imperviousmaterial is a plastic material and is tapered lengthwise so that itdiminishes gradually in thickness from its secured lower end to itsfreely flexible upper end.

15. The partition defined by claim 14, wherein the tapered sheet ofplastic material is a composite laminate constructed from a plurality ofconsolidated sheets graduated in length.

16. A partition for stock vats of rotary pulp molding machines includinga series of foraminous suction molds mounted on the periphery of arotatable drum for movement in succession through pulp stock slurrycontained in a vat thereof, each of said molds being secured to theperiphery of the drum by a retaining ring, said partition comprising aplurality of separate superimposed flexible thin sheets ofsmooth-surfaced impervious material disposed generally vertically andextending entirely transversely across the stock vat, and means forremovably securing the lower ends of said sheets together and to thebottom of the stock vat, the upper ends of said sheets being unsecured,freely flexible, and being bent over into a generally horizontalposition in liquid sealing tangential wiping contact with the surfacesof the drum and the molds advancing therepast, said sheets havingdifferently contoured upper edges adapted to engage different portionsof the surfaces of the drum and the molds advancing therepast.

17. The partition defined by claim 16, wherein the plurality of separatesheets comprising the partition are three sheets of plastic film, theupper edge of one of said sheets being substantially entirely straighttransversely across the vat and adapted to engage only the outermostprojecting surfaces of the advancing molds, the upper edge of another ofsaid sheets being generally straight, but having tab portions adapted toproject into wiping engagement with the surfaces between the molds andtheir retaining rings, and the other of said sheets being generallystraight but having tab portions adapted to project into wipingengagement with the periphery of the drum intervening between adjacentmolds thereon.

18. A partition for stock vats of rotary pulp molding machines includinga series of foraminous suction molds mounted on the periphery of arotatable drum means for movement in succession through pulp stockslurry contained in a vat thereof, comprising an expansible flexiblediaphragm constructed from a sheet of smoothsurfaced wear resistantimpervious material disposed generally vertically and extending entirelytransversely across the stock vat, means for removably securing oppositeedges of the sheet to the bottom of the slurry vat, and means foradmitting fluid under pressure into the interior of the diaphragm tocause expansion thereof, the upper portion of said diaphragm beingdisposed generally horizontally and being in liquid sealing wipingcontact with the surfaces of the molds advancing therepast when thediaphragm is expanded.

19. The partition defined by claim 18, wherein a flexible thin film oftough smooth-surfaced wear resistant plastic material is interposedbetween the expansible dia phragm and the advancing molds and in contacttherewith for preventing wear resulting from the normal wiping contactthereof, and means for securing one end of said film to the bottom ofthe stock vat, the opposite end of said film being unsecured and freelyflexible to conform to the contours of the upper portion of thediaphragm and the surfaces of the advancing molds.

20. In apparatus for molding multi-ply pulp articles, including arotatable drum means having a foraminous suction forming surface on itsperiphery for rotation through a pulp slurry vat mounted below the drummeans, and a plurality of separate compartments provided in the vatadapted to contain slurries of different pulp stocks through which theforming surface of the drum means is advanced successively duringrotation of the drum means, the improvement comprising a flexiblevertical partition mounted in the bottom of the vat and extendingentirely transversely thereacross between said compartments, the upperportion of said vertical partition being mounted in liquid sealingtangential wiping contact with the surface of the drum means advancingtherepast during rotation of the drum means, and means for maintaining adifference in hydrostatic pressure of the slurries in the separatecompartments, thereby effectively preventing intermixing of the slurriesand causing the upper end of the flexible partition to be pressedagainst the surface of the rotating drum means.

21. The apparatus defined by claim 20, wherein the drum means isrotatable in one direction through a pulp slurry vat divided into twoseparate compartments, the forming surface of the drum means beingadvanced in succession through first one and then the other of said twocompartments, and the difference in hydrostatic pressure maintained inthe two compartments results from having the upper level of the slurryin said first compartment at a lower level than of the othercompartment, whereby higher hydrostatic pressure is maintained in thesecond compartment reached by the successively advanced drurn formingsurface during rotation thereof.

References Cited in the file of this patent UNITED STATES PATENTSChaplin Oct. 8, 1929

